The present invention relates to a method and apparatus for repairing fan exit guide vane assemblies for gas turbine engines. More particularly, the present invention relates to a method and apparatus that can be used to make temporary, on-wing repairs to fan exit guide vane assemblies of gas turbine engines.
Fan exit guide vanes (FEGVs) are aerodynamically shaped structures located aft of a gas turbine engine fan and forward of an engine support pylon, installed in a circumferentially spaced, spoke-like arrangement between inner and outer case structures that form a bypass duct. When a gas turbine engine is assembled, the FEGVs are installed between the two case structures before those case structures are connected with the fan. FEGVs help improve the efficiency and thrust output of gas turbine engines by straightening the air stream in the bypass duct flow.
FEGVs can be damaged or liberated during engine operation.
Common causes of damage and liberation include the ingestion of objects that move past the fan and strike one or more FEGVs, the occurrence of transient aerodynamic loads that stress the vanes (e.g., surge events), and the effects of deterioration and normal wear over time. Moreover, once at least one FEGV is liberated, the missing FEGV leads to stresses on adjacent FEGVs frequently leading to the liberation of clusters of adjacent FEGVs. Replacement of original FEGVs in an on-wing position is difficult or impossible. Typically, the only way to remove the FEGVs is to cut them in half.
However, when attempting to replace removed vanes, new FEGVs identical to the originals may not easily fit into the engine while on-wing due to limited clearances and interference from adjacent FEGVs. Thus, known solutions for on-wing repairs include destroying and removing multiple vanes and replacing only a fraction of the original vanes, or alternatively, leaving the engine with zones having no FEGVs. Drawbacks of these known solutions include decreased engine efficiency and regulatory restrictions on flight times for engines having missing or damaged FEGVs. Generally, these known on-wing repairs are only allowed temporarily until off-wing repairs can be completed. Additional on-wing repairs have been attempted, but have generally proven unsuccessful. Off-wing repairs result in substantially greater costs and lost engine flight time than on-wing repairs. Aircraft operators, such as commercial airlines, suffer tremendous losses due to delayed or canceled flights necessitated by off-wing FEGV repairs.
Thus, it is desired to provide a method and apparatus for fan exit guide vane (FEGV) repairs that addresses the problems with existing repair techniques.